I. Field
The subject specification relates generally to wireless communication and, more particularly, to channel state information reporting in wireless systems.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, data, and so on. These systems may be multiple-access systems capable of supporting simultaneous communication of multiple terminals with one or more base stations. Multiple-access communication relies on sharing available system resources (e.g., bandwidth and transmit power). Examples of multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Communication between a terminal in a wireless system (e.g., a multiple-access system) and a base station is effected through transmissions over a wireless link comprised of a forward link and a reverse link. Such communication link may be established via a single-input-single-output (SISO), multiple-input-single-output (MISO), or a multiple-input-multiple-output (MIMO) system. A MIMO system consists of transmitter(s) and receiver(s) equipped, respectively, with multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. SISO and MISO systems are particular instances of a MIMO system. A MIMO channel formed by NT transmit and NR receive antennas may be decomposed into NV independent channels, which are also referred to as spatial channels, where NV≦min{NT,NR}. Each of the NV independent channels corresponds to a dimension. The MIMO system can provide improved performance (e.g., higher throughput, greater capacity, or improved reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
Regardless the peculiarities of the many available wireless communication systems, in each of these systems operation of a wireless device relies on channel quality indicator (CQI) feedback. Access to CQI, which can represent one of various performance metrics, typically facilitates communication resource assignments which are generally accomplished via scheduler in a base station or node B. Accurate CQI reporting can result in excessive overhead or inadequate latency, with the ensuing deterioration in communication. For example, delay-sensitive, high-rate applications like on-line gaming or packet-switched video telephony in a slowly varying channel demand high-frequency CQI reporting, whereas delay sensitive, low-rate applications executing in a fast changing channel can require a large CQI reporting period. Therefore, there exists a tradeoff between CQI reporting latency—controlled primary by reporting frequency—and reporting overhead—largely determined by volume of reported control data. Accordingly, a need exists in the art for flexible CQI reporting, capable of accounting for varied communication scenarios in wireless systems.